Improvement in lightning-rods



UNITED STATES PATENT Ormea .M -uns senz-rrr, ortoNeI'NNi/tfrr, 0111o.

nvlPeovEn/IENTlNlLi-GHTNING-Roos.

Spwii'cation forming` part of Letters Patent No. 5,930, lated May 4,1852.

Be it known that l, JAMES SPRATT, of Gincinnati, in the county otHamilton and State of Ohio, havev invented new and useful'lmincrementsin the lPoints ol' Liglitning-ltods,

t of' which the tol-lowing` is a specification.

'ihe object ol' my improvenientsis to provide a ainst the destructionot' lightning-rod points bg; melting, as they not unfrequently do,i'roin the sudden overcharge of thc electric current.

Having', in the course ol' several `vears perience in the manufactureand setting up ot' lightning-rods, frequently observed instances ol"destruction ot' the points bylig'htniug", and recollecting" that sometime previous a'point Vformed ot' successive layers ot' iron, brass,'and tin, which l had set up in an isolated position for experiment7beingl soon alter; struck by lightning, the outereoveringot' tin meltedott', leaving the brass entirely unaffected 5 and subsequently, duringthe same season, receiving another shock, the brass was melted oli' fromthe iron, which, in its turn, was also left entire, Tuvas led to theplan ot' forming;1 my points ot a number of metals ineased one withinanother, the most fusible to the eutside. The ett'ect of thisarrangement is that the fusing action of an excessive shock oflightningis confined to the outer metallic layer or continu; which in flowing`may be said to carry C! the electric tluid with it, or rather perhaps itreceives in the act ot' mel tin g ail-accession to its conductingpowers; but Whatever may be the true seientic solution ot' thevphenomenon, the fact is demonstrated by experience th at at'- ter themelting' of one layer the next below it is left unscathed and perfect.Thus, by means of a sufllcient numberoflayers-say from three to lfour-apoint may be made capable of surviving as many extraordinary shocksrasanyT one point is likely to encounter, at least during the existence ofany kind of rod such 'as now in use.

The number ot` layers mayvary from two to three, or upward, according tothe desired completeness of the instrument, but the fol lowing I havefound suitable: The innermost point may be of steel, which may beinc-used in brass,the brass in zinc, and, lastly, 'the zinc may becoated with the alloy' of platinum, silver, &c., formerly patented byme, which Vis a superior' conduct-ing medium, and capable ot' receiving'and preserving; a high finish. Each layer should be about fromone-sixteenth to oneeighth of an inch thick, and mar be cast onto thepreceding one.

In the annexed drawings the rod' is shown in section, manufactured asabove described.

Having thus fully described the nature of my improvement, whatclaimtherein as new, and desire to secure by Letters Patent, is-

The formation ot' the point of a lightningrod, ot' three or more metals,incased one within another, the most fusible to the outside, in or derto prevent the destruction ot' the entire point by melting from anovercharge of the electric fluid.

In testimony whereof I have hereunto set my hand before two subscribingwitnesses.

'JAMES SFRATT.

NVitnesses Gno.- H. KNIGHT, EDWARD H. Karene

